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New Aggregation Algorithm for Tandem queue with Finite Buffers
김종환,Hur, Sung Kwan,徐承祿 大邱大學校附設 基礎科學硏究所 1991 基礎科學硏究 Vol.8 No.-
We consider a two-stage fmite tandem queueing system with Poisson arrivals and negative exponential service times. The customer who has completed his service at the first station has to go directlty to the second station. If the queue of the second station is full at the moment of the service completion of the customer at the first station, then the customer receives, another service at the first station. This is repeated until the customer completes a service at the first station at the moment that the second station is not fulL The problem of calculating the steady-state probabilities of this queueing system by the ordinary balance equations is time consuming. We develop an efficient algorithm to obtain the steady-state probabilities that utilize the two-way state aggregation techniques.
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김종환,홍재승 한국스포츠산업경영학회 2003 한국스포츠산업경영학회지 Vol.8 No.2
프로축구리그관중의 만족도와 재구매의도의 상관요인분석에 관한 연구김종환 (중앙대학교), 홍재승 (서울대학교)
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김종환,김동선,예종수,김성은,김응규,허경 인제대학교 1998 仁濟醫學 Vol.19 No.2
풍진은 3일홍역 등으로 알려져 있는 급성 감염 질환으로 특별한 휴유증없이 회복되는 것으로 알려져 있으며 드물게 성인이나 청소년에 있어서 뇌수막염, 혈소판 감소증, 다발성 관절염 등 합병증으로 나타날 수 있다. 우리 나라에서 1996년 봄부터 초여름까지 풍진이 청소년들에게 유행성으로 발병하였다. 저자는 풍진이 유행하던 시기에 양호한 임상 경과를 보인 풍진과 연관된 뇌염 환자 5예를 경험하였기에 보고하는 바이다. In the spring of 1996, We experienced 5 cases of acute encephalitis complicating rubella. They showed convulsions and deteriorated mental states which occurred with vanishing maculopapular rash and low grade fever The CSF study showed pleocytosis, increased protein and normal glucose level. We diagnosed the encephalitis complicating rubella with detection of IgG and IgM in serum. It has been known that rubella encephalitis was a serious complication of rubella, with poor prognosis. The mortality rate reached about 20%, They 5 patients were recovered without any sepuelae.
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Carpentier-Edwards 판막의 장기 술후성적
김종환,이영균,Kim, Jong-Hwan,Lee, Yeong-Gyun 대한흉부심장혈관외과학회 1986 Journal of Chest Surgery (J Chest Surg) Vol.19 No.1
The Carpentier-Edwards porcine xenograft valve was used in 21 patients at Seoul National University Hospital during the period between 1977 and 1979. Twenty-four Carpentier-Edwards valves were implanted along with 2 others. Three patients died within 30 days of operation, an operative mortality rate of 14.3%. Eighteen early survivors were followed up for a total 67.5 patient-years [mean, 45.0$\pm$32.0 months]. There were 2 late deaths with a linealized late mortality rate of 2.96%/patient-year; one died from cerebral bleeding [1.48% bleeding/patient-year] and the other from prosthetic valve endocarditis [1, 48% endocarditis/patient-year]. There was no case of thromboembolism. Two patients developed mitral regurgitation [2.96% failure/patient-year]. Symptomatic improvement was excellent. The actuarial survival rate and the probability of freedom from overall valve failure were 75.3$\pm$9.6% and 80.7$\pm$12.9% at 9 years after surgery respectively. During the period from October, 1968, through June, 1985, 1, 190 substitute heart valves were used in a total of 967 patients at Seoul National University Hospital; of which, 90.9% were either porcine aortic or bovine pericardial xenograft valves. For the evaluation of the xenograft tissue valves, the consecutive patients with lonescu-Shiley valve in the mitral, aortic and both positions, Angell-Shiley valve and Carpentier-Edwards valve were recently studied on the clinical ground. They were 531 patients, and 643 xenograft valves were used. The operative mortality rate was 6.97% and a linealized late mortality rate 2.94%/patient-year. A total of 490 early survivors were followed up for 917.6 patient-years [mean, 22.5 months], and 70% of patients completed the follow-up. The linealized incidences of complications were: 2.29% emboli/patient-year, 1.98% bleeding/patient-year, 1.20% endocarditis/patient-year, and 3.49% failure/patient-year. These clinical resutls are fully comparable with those in the major reports. The durability of the glutaraldehydepreserved xenograft heart valves remains as a great concern and a continuing debate, expecially for the group of patients in the pediatric age. The need of more durable material for the improved tissue valves was also discussed.
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김종환,이영균,Kim, Jong-Hwan,Lee, Yeong-Gyun 대한흉부심장혈관외과학회 1983 Journal of Chest Surgery (J Chest Surg) Vol.16 No.1
Valve replacement in children, aging up to 15 years [Mean 11.g years], has been done at Seoul National University Hospital over the past 14 years since 1968. Fifty-one patients have received 59 artificial valves: 55 bioprosthetic and 4 prosthetic valves. Thirty-one patients [60.8%] had rheumatic heart disease and the remainder [39.2%] had congenital heart disease. Forty-two patients [82.4%] survived operation: 9 patients [17.7%] died within one monfi3 postoperatively and 4 patients [7.8%]during the follow-up period with the overall mortality rate of Thromboembolic complication occurred in 3 patients with 2 deaths: 5.9% embolic rate or 4.68% emboli per patient-year. One patient who had been on coumadin anticoagulation died from cerebral hemorrhage. One mitral Ionescu-Shiley valve failed 19 months after first replacement and this was successfully re-replaced with the same kind of valve. Actuarial survival rate was 59.9% at 4 years after surgery. Thromboembolism-free and valve failure-free survivals were 80.0% and 93.1% respectively. These clinical results in the pediatric age group suggested that valve replacement in children was a serious undertaking with a higher mortality rate than in adults. However, the main superiority on the low thrombogenecity of the xenograft valve over the mechanical one warrants its continuing use until the question of its durability would otherwise be answered by a further study of clinical follow-up.
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김종환 대한흉부심장혈관외과학회 1986 Journal of Chest Surgery (J Chest Surg) Vol.19 No.1
The use of the Angell-Shiley porcine xenograft cardiac valve was limited in number at Seoul National University Hospital chiefly because of the cessation of supply from the manufacturer, Forty-eight Angell-Shiley valves along with the 5 other mechanical or tissue valves were used in 46 patients during the period from 1977 to 1980, and a total of consecutive cases was studied for their early and long-term clinical results. The operative mortality rate was 4.3%; no death after single and 2 deaths after double valve replacement within 30 days of surgery. The 44 early survivors were followed up for a total of 171.6 patient-years and a mean of 46.8$\pm$31.1 months. Four died during the follow-up period with a linealized late mortality rate of 2.33%/patient-year. Four patients had experienced 5 episodes of thromboembolism and one died; a linealized incidence of 2.91% emboli/patient-year. A single case each had a bleeding complication related to the anticoagulants, 0.58% bleeding/patient-year, and prosthetic valve endocarditis, 0.58% endocarditis/patient-year. The clinical improvement was excellent by 70% of the survivors having no cardiac symptoms at the end of the follow-up. The actuarial survival rates were 89.9$\pm$4.9% at 5 years and 69.2$\pm$15.0% at 9 years after surgery. The probabilities of freedom from thromboembolic complication were 92.3$\pm$5.5% and 80.9$\pm$9.0% at 5 and 9 years after surgery. And, the probability of freedom from overall valve failure was 83.4$\pm$6.3% at 5 years and it declined sharply down to 55.9$\pm$22.2% at 9th year of the follow-up. These results are comparable with those in the major reports, except a more accelerated and time-related increases in valve failure after 5 or 6 years after operation with the Angell-Shiley valve. The durability of the xenograft tissue valve remains as the most important debate and the need of more durable tissue valves was also discussed.
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김종환,최성호,Kim, Chong-Kwan,Choi, Seong-Ho 대한치주과학회 1996 Journal of Periodontal & Implant Science Vol.26 No.2
Regeneration of the periodontal tissue destroyed by periodontal disease is one of the final goals of periodontal therapy. In the past few years, periodontists have used various alloplastic grafting materials in an attempt to regenerate bone lost from periodontal disease. These materials have used widely because they have shown to be nontoxic, biologically compatible with surrounding host tissue and chemically similar to bone. The purpose of this study was to investigate the effect of Porous Resorbable Calcium Carbonate and Porous Replamineform Hydroxyapatite on the regeneration of the alveolar bone and the healing of roots transplanted into the periodontally diseased extraction sockets of dogs. The experimental chronic periodontitis was induced by elastic ligatures on the 2nd and 3rd mandibular premolars of 2 adult dogs for 8weeks after surgically creating periodontal defect. The extracted root were split in half along the long-axis, and the extend of plaque exposure was marked on the root surfaces with burs. The roots were inserted in extraction sockets with Porous Resorbable Calcium Carbonate(PRCC) in left side and with Porous Replaminefrom Hydroxyapatite(PRH) in right side. The flaps were sutured to cover the sockets completely. The animals were sacrificed after 12 weeks of healing, and the specimens were examined histologically. The results were as follows: 1. No inflammatory reactions were observed in either groups. 2. Hoot resorption was observed in both groups while the general outline of the roots were maintained. 3. PRCC was almost completely resorbed and replaced with new bone, while R.H.A. was not resorbed & remained encased in newly-formed C-T and alveolar bone. 4. PRH was encapsulated with alveolar bone which has been deposited from apical & lateral area of the sockets, while the coronal portion of the sockets were filled with C-T. 5. In both groups, the resorbed portions of the roots were replaced with new bone. These results suggest that either PRCC or PRH may not interfere with bone formation or healing in extraction sockets, and in some degree, retard the root resorption. Because the roots maintained in anatomy, we think that graft materials prevent the root resorption.
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